Impact Of Different Restorative Materials And Designs On The Biomechanical Response Of The Cracked Tooth: Finite Element Analysis

Objective A cracked tooth model was established by using three-dimensional finite element software and mechanical analysis was carried out to explore the effects of different restoration methods on the stress distribution of cracked teeth.In order to provide some biomechanical basis for the selection of clinical restoration of cracked teeth.Methods A maxillary first molar with a crack line was established.Then applied eight different restoration designs,direct composite resin filling,inlay,onlay,partial-occlusal veneer,partial-occlusal veneer + resin filling,occlusal veneer,crown,crown + resin filling,and four dental materials,composite resin(Filtek Z350),resin nano ceramics(Lava Ultimate),lithium disilicate glass ceramics(E.max),and zirconia all-ceramic(Duolink).Two different forms of loading were tested: a 600 N force parallel to the tooth’s long axis to represent the vertical masticatory force and a 200 N force at a 45° angle to the tooth’s long axis to represent the lateral masticatory force.Under the condition of vertical loading and oblique loading,the stress distribution of the restorations and residual tooth tissue in each model was analyzed using Finite Element Analysis Software(ANSYS17.0).At the same time,the average stresses of 5 points on the crack surface of each model are compared and statistically analyzed.Results The stress concentration of cracked tooth can be significantly improved after restoration,irrespective of the load direction.The occlusal load has a significant effect on the stress response of enamel,but has relatively little effect on the stress response of dentin.Onlay and crown were the most effective in relieving the stress concentration of cracked tooth under vertical loading.Under oblique loading,the most significant effect was observed for the mesio-occlusal veneer and crown.Among all the repair methods,the surface stress of the crack after mesio-occlusal veneer and occlusal veneer restorations was higher than that of other groups.The effect of mesial occlusal veneer+resin filling inside on reducing fracture surface stress was better than that of mesial occlusal veneer,but there was no significant difference between crown+resin filling inside and crown restoration.Compared with the Lava Ultimate materials,E.max shows lower stress value on the surface of the remaining cracks.Conclusion In terms of biomechanics,crown are more effective in alleviating the stress concentration of crack teeth.Considering the principle of minimally invasive restoration,partial-occlusal veneer+resin filling can be selected for restoration.Compared with Lava Ultimate material,E.max material is more suitable for repairing cracked teeth.